AUTOMATISKT FORSTERKNINGSREGLERAT KROMINANSSIGNALFORSTERKARSYSTEM I EN FERGTELEVISIONSMOTTAGARE

摘要

An automatic gain controlled chrominance signal amplifier system for a color television receiver is arranged to process composite chrominance signals having burst and image-representative components. First, second and third amplifier stages are provided for amplifying the image-representative components. The first amplifier also amplifies burst components and is gain controlled in a first closed loop arrangement to maintain a substantially constant amplitude for the burst component and to thereby maintain an appropriate gain for image components. The second and third amplifiers are coupled to the output of the first amplifier. The output of the second amplifier is coupled to a chrominance signal overload detector arranged to respond to image-representative signal components having peak amplitudes greater than a predetermined level. A gain control output provided by the overload detector is coupled to each of the second and third amplifiers to vary their gains in a manner to prevent undesired oversaturation of the displayed image. A further gain control adjustment (e.g., viewer operated) is coupled to the third amplifier but not to the first or second amplifiers. Apparatus is also provided for shifting the operating threshold of the overload detector.